Device for indicating disconnection of lighting means in automobile

ABSTRACT

A device for indicating the disconnection of lighting means in an automobile which insures accurate indication in spite of normal lighting load current variations caused by filament temperature changes, operation sequences, etc. The device includes at least one indicator connected to a power source through a normally closed relay contact that is held open by the normal light load current when there are no disconnected or nonfunctioning lights. The relay coil includes a current coil for carrying the load current and a voltage coil connected in series with a capacitor to cumulatively add to the magnetomotive force of the current coil during an initial period when the light circuit is first switched on to thereby insure an initial opening of the normally closed relay contacts even if some of the light load is disconnected or nonfunctional. In this manner, the normal current variations during the initial period of operation do not cause an erroneous malfunction indication but, rather the current in the current coil after the initial time period is effective to cause accurate malfunction indications.

United States Patent [72] Inventor Yasuhiko Sakurai Kariya-shi, Japan211 Appl. No. 805,127 [22] Filed Mar. 7, 1969 [45] Patented Nov. 23,1971 [73] Assignee Nippon Denso Company Limited Kariya-shi, Japan [32]Priority Mar. 11, 1968 3 3 Japan 3 l 43/8885 [54] DEVICE FOR INDICATINGDISCONNECTION OF LIGHTING MEANS IN AUTOMOBILE 4 Claims, 4 Drawing Figs.

[52] US. Cl 340/251, 315/77, 315/130, 340/80 [51] Int. Cl 1105b 37/03[50] Field of Search 340/52, 54,

3,500,315 3/1970 Shimada 3,504,338 3/1970 Breece ABSTRACT: A device forindicating the disconnection of lighting means in an automobile whichinsures accurate indication in spite of normal lighting load currentvariations caused by filament temperature changes, operation sequences,etc. The device includes at least one indicator connected to a powersource through a normally closed relay contact that is held open by thenormal light load current when there are no disconnected ornonfunctioning lights. The relay coil includes a current coil forcarrying the load current and a voltage coil connected in series with acapacitor to cumulatively add to the magnetomotive force of the currentcoil during an initial period when the light circuit is first switchedon to thereby insure an initial opening of the normally closed relaycontacts even if some of the light load is disconnected ornonfunctional. In this manner, the normal current variations during theinitial period of operation do not cause an erroneous malfunctionindication but, rather the current in the current coil after the initialtime period is effective to cause accurate malfunction indications.

PATENTEUunv 23 mm F/GZ N= NUMBER OF LAMPS SUPPLY VOLTAGE INVENTOR Yasuh}k0 hara;

BY Wm. mb wm ATTY'iRNIfY6 DEVICE FOR INDICATING DISCONNECTION OFLIGHTING MEANS IN AUTOMOBILE BACKGROUND OF THE INVENTION 1. Field of theInvention This invention relates to a disconnection-indicating devicefor informing the driver of a failure in the lighting means in anautomobile or the like due to disconnection or like trouble.

2. Description of the Prior Art Lighting means in an automobile includesheadlights, sidelights, taillights, stoplights, backup lights, licenseplate lights, turn signal lights and the like. In regard to theselights, it has been prior practice to equip only turn signal lights withthe function of indicating the occurrence of disconnection trouble inthe lamps. However, recent rapid popularization of automobiles hasresulted in an increase in traffic accidents and thus poses a serioussocial problem. Among the traffic accidents brought about byautomobiles, accidents due to faulty lighting means are often involvedwith damage to people and this condition must therefore be preventedbefore it occurs. The faulty lighting means must immediately beindicated and be repaired to its normal operating state or the driver isliable to be punished by the police indicating disconnection this sense,the necessity of providing a device for indicating disconnection troubleof lighting means has been progressively recognized.

An indication device of the kind described above is disclosed, forexample, in Japanese Utility Model Publications No. 9432/1959. Accordingto the disclosure, lighting means L and L are grounded at one terminalthereof, and the other terminal of the lighting means L and L isconnected through a current coil 3 and a switch 2 with a power supply 1as shown in FIG. 1. The switch 2 is interlocked with a switch 2 which isconnected with an indication lamp or indicator 5 through a normallyclosed contact 4 which is driven by magnetic force caused around currentcoil 3. However, the indication device having such a structure issubject to various limitations in practical use since a decrease in theload current of the lighting means is detected by the combination of thecurrent coil 3 and the normally closed contact 4 driven by magneticforce produced by the current coil 3. More precisely, the lighting meansused in the device of this kind includes generally a plurality ofincandescent lamps which exhibits a very great difference intemperatures between the deenergized state of the lamp and the energizedstate. In the early stage of energization of the lamp, there flows anexcessively large current which is from to times the regular energizingcurrent depending on the specification of the lamp as well as theconditions of the circuit including the lamp. The excessively largecurrent occurring in the early stage of lamp energization is generallyreferred to as overflow current. The overflow current either does notflow at all or it takes on a relatively smaller value such as only twoor three the regular energizing current when the lamp is energized aftera short interruption thereof or when the lamp is preheated by a darkcurrent. Those in the art will appreciate that the load current of thelamp has such a peculiar property.

Suppose that the operating current (that is, the current which makes thenormally closed contact 4 open) of the simple current relay shown inFIG. I is slightly smaller than the rated current of the lamp load. Insuch a case, the current relay is operated by the starting overflowcurrent when switching the lamp load on" thereby making the normallyclosed contact 4 open even if one of the lamps is disconnected; once thenormally closed contact 4 is open, it can be kept in its open positionby a holding current which is usually much smaller than the operatingcurrent; therefore, the normally closed contact 4 thus urged to its openposition by the overflow current occurring in the state in which one ofthe lamps flowing through may be held in that position by a reduced loadcurrent flowing through the remaining nondefective lamps. Similarly,when the operating current of the current relay; that is, the overflowcurrent of the lamps in a usual application is employ ed as the baselevel for detecting any variation in the lamp load, the normally closedcontact 4 cannot be driven to its open position in case the switch isintermittently manipulated and there is no overflow current in spite ofthe fact that the load is normal. Further, when the holding current ofthe current relay (which corresponds to the magnetomotive force forholding the relay in open position); that is, the regular current of thelamps in their normally loaded state, is employed as the base level fordetecting any variation in lamp load; the operating current of thecurrent relay is reached only in the case in which the overflow currentappears in the lamps in their normally loaded state. Thus, the relay mayperform a defective operation unless the overflow current appears in thenormally loaded state of the lamps.

For the reasons described above, the lamp disconnection indicationdevice having a detecting element in the form of a single current coilis inevitably subject to a great limitation in practical use. Since theoverflow current appearing in the lamp causes a restriction to thesuccessful detection of the lamp load, a detection device which iscompletely free from the effect of the overflow current will functionmore satisfactorily.

The voltage load current characteristic of a 20-watt l2-volt lamp isshown in FIG. 2. As seen in FIG. 2, the load current of the lamp variesgenerally in proportion to the 0.56th power of the voltage and thus avariation in the current relative to the voltage is relatively small. Interms of the regular current, the amperage of two lamps at 16 volts isequal to the amperage of three lamps at 7.3 volts. Theoreticallyspeaking, a detecting device, if it is not influenced from the overflowcurrent, can detect at least a load variation equivalent to one-third ofthe normal load current, even if the supply voltage changes from 10volts to 15.6 volts as above mentioned.

SUMMARY OF THE INVENTION It is a primary object of the present inventionto provide a device for indicating disconnection of lighting means in anautomobile comprising a current coil through which the lead current ofthe lighting means passes, a voltage coil having a capacitor connectedin series therewith, and a normally closed contact adapted to be drivento its open position by the initial attraction force developed by saidcurrent and voltage coils, wherein the magnetomotive force for holdingthe normally closed contact in its open position is selected as thelevel for detecting any variation in the load.

In accordance with the present invention, a departure from the regularcurrent flowing through the lamps is utilized to detect a disconnectionoccurring in the lamps so as to provide the ability of detection over avery wide range, and a voltage coil is provided to increase the initialmagnetomotive force so that the device can operate reliably withoutbeing affected by the energized state of the load and independently ofthe presence or absence of overflow current. Further, in accordance withthe present invention, the indication devices may be connected inparallel and a single indicating lamp or indicator may be provided sothat a disconnection trouble occurring in any one of the lamps of manysystems can be detected and indicated on the single indicating lamp orindicator. Up to three lamps can be incorporated in the same system.Thus, the disconnection-indicating device of the present invention canbe applied to the prior art wiring system of an automobile withoutmodifying the wiring system In accordance with the present invention, adiode is connected in parallel with the voltage coil in a directionopposite to the direction of current flow so that the diode acts toeliminate the ojectionable defective operation of the device due to anabrupt drop of the voltage or the power supply in a short period oftime. By virtue of the reliable operation of the device in the mannerdescribed above, the devices is very useful as a safety device for anautomobile.

BRIEF DESCRIPTION OF THE DRAWINGS:

FIG. 1 is an electrical connection diagram of a prior artdisconnection-indicating device as described previously.

F IG. 2 is a graphic illustrated of the voltage current characteristicof an incandescent lamp load.

FIG. 3 is an electrical connection diagram of an embodiment of thepresent invention.

H6. 4 is an electrical connection diagram of a more practical embodimentof the present invention for use in an automobile.

DESCRIPTION OF THE PREFERRED EMBODlMENTS Referring to FIG. 3 whereinlike reference numerals are used to denote like parts appearing in FIG.1, the disconnection-indicating device according to the presentinvention includes a power supply 1, a switch 2, a current coil 3, anormally closed contact 4, an indicating lamp 5, an indicator 5', avoltage coil 6, an electrolytic capacitor 7, and a diode 8. Lamps L Land L such as stoplights or taillights of an automobile are connectedwith the current coil 3. The current coil 3 and the voltage coil 6 arearranged to be in the same phase electromagnetically so as to drive thenormally closed contact 4 to its open position.

In operation, the switch 2 is closed to supply the voltage of the powersupply 1 to the lamps L,, L and L through the current coil 3 thereby toenergize the lamps. At the same time, the capacitor 7 is charged by thecurrent supplied through the voltage coil 6, and the charging currentdevelops an attraction force in the voltage coil 6. More precisely, anattraction force is developed in both the current coil 3 and the voltagecoil 6 when the switch 2 is closed, and the charging current for thecapacitor 7 produces a large magnetomotive force in the early stage ofthe closure of the switch 2 thereby to drive the normally closed contact4 to its open position. Thus, since the normally closed contact 4 isdriven to its open position as soon as the switch 2 is closed, theindicating lamp 5 is not energized and the indicator 5' does notoperate. After the normally closed contact 4 in its open position it iskept in such a position so long as the magnetomotive force for holdingthe normally closed contact 4 in its open position is continuouslyapplied. Therefore, the magnetomotive force of this magnitude may beselected as the level for detecting any unusual condition of the load sothat the normally closed contact 4 can be kept in its open position withthe load current with which all the lamps L L and L, are normallyenergized, while the normally closed contact 4 can be restored to itsclosed position again when a disconnection occurs in any of these lampsL L and L in this latter case, the indicating lamp 5 is energized or theindicator 5" is operated to inform the driver of the occurrence ofdisconnection trouble in the lamps.

Referring to FIG. 4 wherein like reference numerals are used to denotelike parts appearing in FIG. 3, reference symbols H, P, T, R, B and Sdesignate headlights, parking lights, taillights, a license plate light,backup lights and stoplights, respectively. Suffixes are attached to thereference numerals to clearly show the systems to which the respectiveelements belong. The diode 8 shown in FIGS. 3 and 4 is provided for thepurpose of releasing the attraction force of the voltage coil 6 duringthe discharge of the capacitor 7. Thus, the diode 8 acts to prevent adefective operation of the device due to an abrupt drop of the voltageof the power supply 1 in a short period of time.

I claim:

l. A device for indicating disconnection or failure of a lighting meansin a automobile, said device comprising:

a plurality of lighting means having a normal load current after aninitial energizing period,

at least one indicator,

a normally closed relay contact in series circuit with said indicatorand a DC power source whereby an indication is given whenever said relaycontact is closed,

a current coil means for providing a first electromagnetic force tendingto operate said relay contact from the closed position to an openposition, said current coil means being connected between said DC powersource and said plurality of lighting means, and a voltage COll meansfor providing a second electromagnetic force in the same sense as saidfirst force also tending to operate said relay contact cumulatively withsaid current coil means, said voltage means being connected through acapacitor across said DC power source whereby said relay contact isalways opened during said initial energizing period,

said first electromagnetic force produced by the normal load current ofsaid lighting means after said initial energizing period being sightlylarger than the electromagnetic force necessary for holding said relaycontact in the open position whereby said indication will be givenaccurately upon even a slight reduction in said normal load current.

2. A device as in claim 1 wherein a diode is connected in parallel withsaid voltage coil means with the forward diode current normally carriedby said voltage coil means to bypass reverse currents in case the DCpower source is abruptly reduced.

3. in a light-load-failure-indicating device comprising normally closedrelay contacts connected to an indicator and held open by the normaloperating current of a lighting load including a plurality of lightingmeans connected to a DC power source through a current-sensitive coil ofthe relay whereby a decrease in lighting load current caused by a lightfailure of a lighting means causes release and closing of the relaycontacts to energize the indicator, an improvement comprising:

a series-connected voltage coil and capacitor combination also connectedacross said power source,

said voltage coil being wound on said relay and connected to produce anelectromagnetic force in the same sense as that produced by said currentcoil whereby for an initial time period, the cumulative electromagneticforces from said voltage coil and said current coil insure an initialopening of said relay contacts even if some of the lighting load isnonoperative, and

said electromagnetic force produced by a normal lighting load currentafter said initial time period being slightly larger than theelectromagnetic force necessary for holding said relay contacts in theopen position whereby said indication will be given accurately upon evena slight reduction in said normal load current.

4. A lightload-failure-indicating device as in claim 3 furthercomprising a diode connected in parallel with said voltage coil and in asense opposite to the normal direction of current through said voltagecoil to bypass reverse currents in case the DC power source is abruptlyreduced.

UNITED STATES PATEN? GFFEQE QERTEICATEE 6E GRRECTEON Patent No 1 623,055 Dated November 23, 1971 Inventor(s) Yaguhiko SAKURA I It iscertified that error appears in the above-icientified patent and thatsaid Letters Patent are hereby corrected as shown below:

? In the heaoing the Priority "Mar 11, 1968 Japan 3/8885" should read--Mar. 11, 1.968 Japan Signed and sealed this 23rd day of May 19?.2,

. 1"": A; QSJLAL) Ltest:

33mm PLFLLTGEElg 38.. ROBERT GOTTSCHALK Eat-testing Officer Commissionerof Patents URM F G-10 w \W- USCOMM-DC sows-Pas

1. A device for indicating disconnection or failure of a lighting meansin a automobile, said device comprising: a plurality of lighting meanshaving a normal load current after an initial energizing period, atleast one indicator, a normally closed relay contact in series circuitwith said indicator and a DC power source whereby an indication is givenwhenever said relay contact is closed, a current coil means forproviding a first electromagnetic force tending to operate said relaycontact from the closed position to an open position, said current coilmeans being connected between said DC power source and said plurality oflighting means, and a voltage coil means for providing a secondelectromagnetic force in the same sense as said first force also tendingto operate said relay contact cumulatively with said current coil means,said voltage means being connected through a capacitor across said DCpower source whereby said relay contact is always opened during saidinitial energizing period, said first electromagnetic force produced bythe normal load current of said lighting means after said initialenergizing period being sightly larger than the electromagnetic forcenecessary for holding said relay contact in the open position wherebysaid indication will be given accurately upon even a slight reduction insaid normal load current.
 2. A device as in claim 1 wherein a diode isconnected in parallel with said voltage coil means with the forwarddiode current direction being opposite to the direction of the currentnormally carried by said voltage coil means to bypass reverse currentsin case the DC power source is abruptly reduced.
 3. In alight-load-failure-indicating device comprising normally closed relaycontacts connected to an indicator and held open by the normal operatingcurrent of a lighting load including a plurality of lighting meansconnected to a DC power source through a current-sensitive coil of therelay whereby a decrease in lighting load current caused by a lightfailure of a lighting means causes release and closing of the relaycontacts to energize the indicator, an improvement comprising: aseries-connected voltage coil and capacitor combinatiOn also connectedacross said power source, said voltage coil being wound on said relayand connected to produce an electromagnetic force in the same sense asthat produced by said current coil whereby for an initial time period,the cumulative electromagnetic forces from said voltage coil and saidcurrent coil insure an initial opening of said relay contacts even ifsome of the lighting load is nonoperative, and said electromagneticforce produced by a normal lighting load current after said initial timeperiod being slightly larger than the electromagnetic force necessaryfor holding said relay contacts in the open position whereby saidindication will be given accurately upon even a slight reduction in saidnormal load current.
 4. A light-load-failure-indicating device as inclaim 3 further comprising a diode connected in parallel with saidvoltage coil and in a sense opposite to the normal direction of currentthrough said voltage coil to bypass reverse currents in case the DCpower source is abruptly reduced.